Of course I believe in God. The world and all that is in the earth including mankind will not exist if there is no God. He is the creator of heaven and earth.  Everything started in Him and ended in Him. We owe our life to Him so we have to worship Him as our way of gratitude to our Lord. Our life will be miserable and meaningless if there is no God. Believe in God even if you don't see Him.  That's faith.